Dual extraction of grease, glue, and gelatin



July 31, 1951 R. s. TOUR 2,562,221

DUAL EXTRACTION oF GREASE, GLUE AND CELATIN Filed Feb. 10, 194s Y 'll/1111, \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\`\vA\\\\\\\\\\ IN VEN TOR.

' A BY f f 2596, Mgejmy/M/MQM Patented July 31, l195 DUAL EXTRACTION 0F GREASE, GLUE, AND

' GELATIN Reuben S. Tour, Cincinnati, Ohio, assigner to Darling & Company, Chicago, Ill., a corporation of Illinois Application February 1o, 194s, serial No. 7,485

1s claims. (ci. 26o-11s) This invention relates to a process of extracting grease and glue or gelatin. The invention is disclosed particularly in relation to the manufacture of hide glue since its advantages are mostA useful in respect to such production, but is also `adapted for the production of bone glue and infdustrial and edible gelatin, depending upon lthe 'natureof the raw material which is employed.

Hide glue is commonly manufactured from vhide and animal substances, either raw or treated with lime or tanning agents. These materials often are referred to in the industry as hide trimf'mings, pates, ears, lips,` snouts, tail stubs; raw hide, gara blanca, that is, dry limed iieshings,

coney stock, chrome pieces, splits and shavings, sinews, tendons, and so-called fleshings, which are small pieces trimmed from hides to which some flesh of the animal adheres. In this specication, for purposes of convenience, the term hide stock is used to denote any of the mate- Arials commonly used in hide glue manufacture which can be plumped or detanned and plumped rfor glue extraction.

Animal glue, whether derived from hide stock, bone, fleshings or the like, essentially is gelatin which has been obtained by the hydration ofrcollagen, a protein occurring naturally in the hide terms of the strength of the gel which the glue is capable of producing When mixed with a predetermined amount of Water vand held at a predetermined cool temperature for a predetermined time. Thus, animal glue'is gradedas to quality in terms of gel or bloom strength. Thergelatin y .formed by the hydrolysis of the collagen is susceptible to further hydrolysis which is destructive in that it releases amino `acids and other ldegradation products, the presence of Which impairs Vthe gel strength and value of the glue.

Hide stock, bone and otheranimal substances also contain grease Which is of substantial commercial value, so in the past the process of manufacturing hide glue has been conducted to obtain animal grease as a by-product. While the plastic or liquid nature, thegreases obtained in 'glue production also sometimes include the'hig'h titre semi-solid fats present in some types of stock. The past process 0f mariufaoimrir-igv glue has been as follows:

term grease commonly suggests aproduct ofaV jperature.

Wastes from tanneries and slaughter 'house (scraps of hide, ears, lips, tails, tendons, etc.) are placed in large vats and treated with a limesuspension or slurry for a period of from two lto thirty Weeks. The lime saponies a part ofthe fatty matter, forming insoluble soaps, and partially dissolves the non-collagens, such as blood, flesh and coriin. If the liming is continued to'o long, the stock itself dissolves, but as generally determined by experience, the treatment-is stopped when the pieces have the proper feel. This treatment has the effect of plumpingfwthe hide,'making it loose and soft, and making the collagen more easily accessible for hydrolysis and gelatin formation, While also making the grease in the stock more readily available. Thus, the plumping is a necessary step preparatory to further treatment of the hide stock. Also, the lime, besides plumping the hides, permits limited storage of the material until it is needed, the high alkalinity reducing bacterial decomposition.

' When the raw material is ready to be processed 'to obtain glue andV fat, it is freed from all traces vof lime by careful, prolonged, and repeated Washing in the cold, first with Water, and subsequently with an acid, such as dilute sulfuric acid, which neutralizes the lime and converts some' of the lime soaps to fatty acids. The stock, after acidulation, is again washed, or Washed andr neutralized with alkaline materials in the cold, to remove excess acid preceding the heated uhy,- drolysis operation to follow. These Washes of the stock may cause considerable loss of grease and some glue from the hide stock. 'If any lime or'too much acid remains in the hide stock, thenfbpth 4the glue and the fats will be contaminated and inferior. These operations are conducted, batchwise, in large tanks equipped with heavy edge-runner wheels or drums which slowly and gradually work the stock to facilitate infusion of fthe treating'liquids, and the liberation of some 4of the wfat therefrom. Even modern-present day glue plants comprise many of these tanks, often lattended by operators who 'manually load the 'material from Wheelbarrows and who manually skim off the fat which floats atthe surface The labor cost is high. 5"

" The 'rawj material, after these treatments, is next transferred, together with the i proper amount of water,.to open pans or kettles which are usually provided with false, sieve-like bottoms and are heated by steam coils or by a steam jacket,the Water being kept at a simmering tem- 'I'he glue forms slowly and dissolves 'in'th'e hot Water, but the hair and the meat r'emain suspended. Fats flow to the surface and are skimmed o. Long boiling or cooking and excessive temperatures must be avoided as both impair the adhesive property of the glue. At intervals, the glue liquor is filtered off through the sieve-like bottom, and run into a vacuum pan for concentration.

Early methods of glue extraction from hide stock, since superseded, employed cooking the hide stock in closed kettles until practically all of the collagen in the stock had been hydrolyzed. However, the time necessary to diffuse out the last portions was so great that much of the earlier hydrolyzed gelatin was converted to degraded forms and thus, much of its `value was lost. In the more recent methods of extraction, attempt is made to avoid excessive hydrolysis of the gelatin first extracted, and to 'improve the glue yield, by subjecting the material to rive or more separate cooks, with a withdrawal of the glue solution after each to decrease secondary hydrolysis or degradation. This relatively improved technique. results in yields of 90% of the available glue, but, at best, only a 60 to '70% yield of the grease originally present in the hide can be recovered. A considerable quantity of the grease thatrcannot be obtained in the cooking because of the inefcient means of extraction remains in the residue (hair tankage) in the kettles. Some grease has also been lost in the wash water during the previous washing and. acidulation of the stock.

The objective of the present invention has been to provide a process of obtaining gelatin or glue and animal fat from hide stock or other suitable raw material, such that stronger and more valuable glue, and a larger percentage of animal fat are recovered in much less time than heretofore has been required.

Microscopic examination of hide stock reveals a brous structure containing grease cells dispersed throughout the entire section. These grease cells are water repellent and tend to inhibit the washing out of the hydrolyzed collagen which exists, initially after formation, as a heavy,

viscous, sticky colloidal dispersion within the hide stock. It has been determined that when the hide stock is cooked with water alone, then the presence of the grease cells severely hinders extraction of the glue. in the literature, the kwashed hide stock is cooked in a grease solvent, then the colloidal solution of the glue retards the wetting and penetration of the grease solvent.

Brieiiy, the process of this invention comprises subjecting the hide stock alternately and succes'- sively to exposure to water, and to fat or grease solvent at a temperature adapted to promote hydration of the collagen. By this method the hide stock is repeatedly subjected to the action of the solvent, which progressively removes fat, and to the action of the water, which progressively washes out gelatin. Thus, the hide stock is opened up progressively by the extracting action of two substantially immiscible specific solvents to which the hide stock is alternately and successively exposed. As a result of such treatment, high Yyields of glue and grease are obtained, in convenient separable condition, in but a fraction of the time which heretofore has been considered necessary.v

This type of exposure and treatment may be provided by various forms of equipment and apparatus such as -mechanical means for alternating the hide stock in separate tanks of water @1.111

If, las has been proposed solvent, or means of percolating one liquid in dispersed phase through the hide stock immersed in a continuous phase of the other liquid. As a practical matter, it has also been determined that mechanical Iagitation greatly accelerates the diffusion of the newly formed thick glue out of the hide stock. All of the requisites of the process are satisfied expeditiously by tumbling the hide stock through a layer of solvent and a layer of water in a rotating perforated drum submerged in the two layers within an external stationary cylindrical shell; alternate exposure of the stock to water and solvent enables hydrolysis and fat extraction to Occur with best eiciency and minimum interference between the two steps.

The solvent employed in this process must be a good solvent for animal fat, should be substantially immiscible with water, and should not dissolve gelatin; otherwise, solvent Iand fat would contaminate the liberated glue or glue would be lost in the solvent and fat. Also, the solvent must be of such nature that it does not tend unduly to emulsify with the water layer. In general, hydrocarbon solvents are particularly suitable for the practice .of this process in that most of them have the properties requisite. From the point of view of economy and fat protection in the solvent recovery, a solvent having relatively low boiling point is recommended, such as naphtha or heptane. If diminution of nre hazards warrants the greater expense of solvent recovery, such chlorinated solvents as carbon tetrachloride, trichlorethylene, or perchlorethylene also may be utilized in the process; however, it is to be noted that in such instances the solvent, being heavier than Water, will constitute the lower rather than the supernatant layer. In either event, the two media, one for extracting grease and the other for hydrolyzing collagen and extracting the hydrolysis products, are substantially in layer relationship to one another. For purposes of convenience in the description, the solvent throughout this specication is re- `ferred to as the supernatant layer, but the invention, as just indicated, is not limited in this respect.

In the process of the present invention, the hide stock is loaded into the extractor (later described in more detail) in which washing, acidulation and cooking are all accomplished, in the presence of a solvent layerY and a water layer. Due to the tumbling, the cold initial wash is rapid and liberated grease collects in the solvent layer. The same applies to the cold acidulation that follows, as well as rto the `final wash following acidulation. The solvent is allowed to remain in the equipment .after the last wash, and water is added for the glue cooking.

Cooking of the hide stock in the new process may be conducted at a temperature of to 210 F. in the atmosphere, or at higher temperatures if the cooking is conducted under pressure but the temperature is preferably not permitted to rise higher than F. because the secondary decomposition of gelatin becomes increasingly objectionable as temperatures are elevated. Although higher temperatures are commonly used in the present standard methods of manufacture of the hide glue of commerce, it is desirable that the temperature be kept below 180 F. as indi-y cated, if a superior strength glue is desired. If greater strength glue is not required, as in the case of glue used for sizing or other purposes not involving the factor of. strength then the pro.-

substantially greater strength than the hide glues at present on the market. The fat solvent need not be changed for each cook inasmuch as the solvent remains fat receptive.

The pH value of the solution in which hide stock is cooked should be substantially 3 to 4 for the iirst cook and progressively higher for the second, third, or more cooks up to a pH of approximately 6. The pH of the cooking waters and pI-I control are important factors in the new process. Low pH hastens de-saponification of mineral soaps as well as decrepitation of the stock and rate ofglue extraction, but too low pH brings about degradation of the glue and poor gel strength.

'I'he accompanying drawing shows, somewhat diagrammatically, apparatus suitable for practicing the process. In the drawing:

Figure 1 is a longitudinal sectional view taken through the apparatus, While Figure 2 is a crosssectional view. The equipment shown in the drawing consists of a closed cylindrical 'casing 2 having a door or opening 3 through which hide stock may be loaded. A perforated drum 4, hav- Ving a door 5,.is rotatably disposed within the cyly inder 2, and the doors are arranged so they may be positioned in alignment for charging a load of hide stock into a drum 4. The shaft 6 of the drum 4 passes through the ends of the enclosing cylinder which is equipped with bearings 1, and the shaft is preferably driven at a relatively slow rate, for example 1 to 5 R. P. M. as bymeans of a belt 8 from a suitable power source. Any conventional driving means desired may be employed and the drum may be rotated either continuously in one direction or intermittently, rst in one direction and then in the other. Inside ofthe drum 4, one or mo-re lifts l0 are circumferentially disposed, the purpose of these being to carry the hide stock upwardly to a position above the level of the liquid in the cylinder 2 so that it will fall through the liquid. Attached to the bottom portion of the cylinder are two pipes Il and l2, the former for admitting fresh water, the latter for withdrawing the gelatin solution to evaporation pans. Above these two pipes are two additional pipes i3 and |`4, the former for admitting fresh solvent into the container, the second for withdrawing the solvent-fat solution from the container to the still Where the fat and solvent are recovered. Pipe I 4, Within the container 2, may be equipped with a suitable swing pipe (not shown) rfor decantation lof the upper layer. Heat may be applied to the liquid in the equipment in any suitable manner, as, for example, by jacketing of the outer cylinder 2 or by steam coils or open steam injection. The equipment may be operated at atmospheric pressure, or under higher pressure for higher temperatures.

. During cookingV of the stock, the temperature may reach the boiling point of the water-solvent admixture as determined by the pressure, in which event vapors will be liberated. For economy in the operation of the apparatus, these vapors may be led from the equipment through a vent pipe I5 to a reflux condenser whereby both condensed solvent and water may be returned for reuse. It is to be noted that the boiling point of the watersolvent system in the apparatus will be less than the boiling point of either the water or the solvent, in the use of such solvents as heptane or the like. In fact, this phenomenon provides a very usefulcontrol in the practice of the invention, inasmuch as the temperature at which extraction is conducted is self-governing at a point below the temperature at which degradation of gelatin becomes serious.

The rotating drum should be substantially immersed in the liquid consisting of the water and solvent layers, with the solvent constituting approximately 20 to 50% or more of the total liquid, depending on the nature and fat content of the raw material. but appropriate choice in correlation with other conditions is a factor in the overall efficiency of the process. Thus, the solvent quota may be increased if the fat content of the stock is high, and vice versa.

y An important feature of this invention resides in the fact that the washing and acidulation of the hide stock, as well as the later cooking, can be expediently performed in the described equipment, with washing, acidulation and cooking all accelerated by the alternating contact of the stock with the dual solvents, and by the mechanical agitation. As previously stated, the hide stock, after being treated with lime, must be thoroughly Washed to remove all lime and mustbe acidulated before the cooking operation is commenced. Washing and tumbling the hide stock through 'the layer of solvent very much speeds up the washing. YIf the acid in the wash water converts any lime soap in the hide stock to free fatty acid, this is dissolved by the solvent together with whatever free fat is exposed to the solvent. Such action tends to open up the hide stock by removing the predominance of fat.

In previous conventional processes, washing and accidulation of the hide stock requires from 20 to 40 hours. By the present procedure, this operation may be performed in a period of only 2 to 4 hours, using a rotary washer and cooker. In other words, the process of this invention cuts the washing time to about 10% of current practice.

As an example, limed fleshings, one type of hide stock, usually contains about 8 to 12% grease. The most modern methods of extraction require 36 to 48 hours cooking time, in addition to the 20 to 40 hours required for washing and acidulation, to extract some of the potentially available glue and 60 to 70% of the available fat. The

present process not only extracts 90 to 95% of the available glue, but also 90 to 95% of the fat and grease present in the eshings in 3 to 5 hours of cooking time after the 2 to 4 hours washing and acidulation.

In the process of this invention, preferably, the hide stock is given two, three, or at most four cooks of about one hour each, whereas current methods require five or six cooks of the stock, totalling 36 to 48 hours. Thus, the process reduces the cooking to substantially less than onetenth (11s) of the time required by present practice.

f Hide glues obtained by the common methods of kettle cooking seldom attain a jelly test of over 400 grams for the rst cook, and the average of the product of current practices is about 250 to 300 grams. The average strength of the glue produced by the method of this invention, is,

on the jelly test, 400 to 600 grams, depending These proportions are not critical on equivalent stock. Th 5, the practice of this invention, in comparison with present practice, yields a superior glue in a substantially shorter time, recovers a greater percentage of fat, requires less equipment, and ieiver handlings of the hide stock.

While the example just disclosed typically i1- lustrates the utilization of this invention in the manufacture of glue, the invention as previously indicated equally be used for the manufacture of edible and inedible grades of gelatin, by the procedure described. Thus, the terms glue gelatin are used interchangeably in the spcciiication and in the claims which follow.

The process also is applicable to the manufacture of glue from bones, according to the procedure which has been described. T n this respect, however, extraction oi the gelatin and grease from the bones is hastened by conducting the operations at super-atmospheric pressures with attendant higher temperatures. While higher temperatures are usually undesirable in the extraction of glue from hide stocks, the evidence which is available at present indicates that the collagen found in bones is of such a nature as to make it desirable to conduct the extraction at somewhat higher temperatures than those utilized when operating upon hide stock.

Having described my invention, I claim:

l. The method of obtaining glue and grease from animal substances which comprises, treating the animal substances alternately and repeatedly with a solvent for glue at a temperature sufficiently high to convert collagen to gelatin, and with a solvent for grease, which solvent is substantially immiscible in the glue solvent and does not substantially dissolve gelatin.

2. The method of obtaining glue and grease from animal substances which comprises, treating the animal substances alternately and repeatedly With aqueous solvent for glue at a temperature adapted to convert collagen in the animal substances into gelatin and with an organic solvent for grease substantially immiscible in the aqueous glue solvent by tumbling the animal substances through the two solvents which are in layer relationship to each other.

3. The method of deriving glue and grease from animal substances containing collagen and grease, which method comprises, subjecting the animal substances alternately and repeatedly to Water at a temperature suilicient to convert collagen in the animal substances into glue, and to a subsantially water immiscible grease-receptive solvent, the said solvent overlying the Water as a supernatant layer.

4. The method oi deriving glue and grease from animal substances containing collagen and grease, which method comprises, subjecting the animal substances alternately and repeatedly to Water at a temperature sufficientto convert collagen in the animal substances into glue, and to a substantially Water immiscible grease-receptive solvent for a period ci" time sufficient for the Water to extract hydrolyzed collagen from the animal substances, and the solvent to extract grease therefrom.

5. The method of deriving glue and grease from animal substances containing collagen and grease, which method comprises, treating the animal substances alternately and repeatedly with water at a temperature sufliciently elevated to convert collagen in the animal substances into glue, and with a hydrocarbon solvent for the purpose of dissolving grease therein as liberated 8.. from the animal substance during the cooking thereof in the Water.

6. The method of obtaining glue and grease from hide stock which comprises, cooking the hide stock in Water at a temperature of substantially 179 to 189 F. and repeatedly exposing the hide stock during said cooking, to the action of a grease solvent which is. substantially immiscible with Water and is not a good solvent for gelatin.

'7. The method of obtaining glue and grease from hide stock which comprises, cooking and agitating the hide stock in water at a temperature above approximately J F., physically agitating the hide stock during the cooking process, and alternately and repeatedly exposing the hide stock during cooking to a grease solvent which is substantially iminiscible with water and is not a good solvent for gelatin.

8. The method oi obtaining glue and grease from hide stock which comprises, cooking and agitating the hide stock in water at a temperature above approximately 140 F., and physically agita-ting the hide stock during the cooking process by tumbling the hide stock through a layer of grease solvent and a layer of cooking water, said grease solvent being substantially immiscible with water and not a good solvent lor the gelatin.

9. The method oi obtaining glue and grease from hide stock which comprises, treating the hide stock alternately and repeatedly With Water at a temperature adapted to convert collagen in the hide stock into gelatin, and with a substantialli7 'vvate miniscible solvent for grease, by tumbling the hide stock through layers of solvent and water, the hydrogen ion concentration of the water being controlled and maintained at values optimum for hydrolyzing collagen and extracting grease.

l0. The method ci obtaining glue and grease trom alkaline hide stock which comprises, neutralizing the hide stock, cooking and agitating the hide stock in iva-ter at a temperature above approximately 140 F., physically agitating the hide stock during the cooking process While repeatedly exposing the hide stock during cooking to a layer of grease solvent which is substantially iminiscible witi the Water layer and is not a good solvent for gelatin, the hydrogen ion concentration oi the water throughout the cooking process being maintained at a value between approximately 3.0 and 6.0.

ll. The method of deriving glue and grease from animal substances which previously have been limed, which method comprises, Washing the animal substances in water which resides in layer relationship to Water immiscible grease-receptive solvent, and thereby removing lime from the animal substances and partially liberating grease thereirom, removing the wash Water, subsequently cooking the animal substances in Water at temperatures suicient to convert collagen present in the animal substances into gelatin, While repeatedly and successively exposing the animal substances during cooking to the water and to the grease-receptive solvent, thereby completing liberation of grease from the animal substances and simultaneously converting collagen to gelatin and finally separating the grease-laden solvent from the gelatin-laden water.

l2. The method of deriving glue and grease from animal substances which previously have been limed, which method comprises, washing the animal substances in water which resides in layer relationship to substantially Water immiscible grease-receptive solvent, and thereby removing lime from the animal substances and partially liberating grease therefrom, removing the Wash Water, neutralizing the hide stock while it is in contact with the solvent, subsequently cooking the animal substances in Water at ternperatures suiiicient to convert collagen present in the animal substances into gelatin, while repeatedly and successively exposing the animal substances during cooking to the water and to the grease-receptive solvent, thereby completing liberation of grease from the animal substances and simultaneously converting collagen to gelatin, and nally separating the grease-laden solvent from the gelatin-laden water.

13. A method of deriving grease, and a material of the class consisting of gelatin and glue, from animal substances containing grease and collagen, which method comprises, treating the animal substances alternately and repeatedly with hot Water and with a substantially water immiscible grease solvent for a period of timek suiiicient for the water to hydrolyze collagen and thereby to Separate it from the animal substances, and the solvent to dissolve grease and thereby separate it from the animal substances, and subsequently separating the grease-daden solvent from the water containing hydrolyzed collagen.

14. A method of deriving grease, and a material of the class consisting of gelatin and glue, from animal substances containing grease and collagen, which method comprises, treating the animal substances alternately and repeatedly with hot water and with grease solvent for a period of time sufficient for the Water to hydrolyze collagen and thereby to separate it from the animal substances, and the solvent to dissolve grease and thereby separate it from the animal substances, and subsequently separating the grease-laden solvent from the water containing hydrolyzed collagen, the said solvent being substantially immiscible With Water.

15. A method of deriving grease, and a material of the class consisting of gelatin and glue, from animal substances containing grease and collagen, which method comprises, treating the animal substances alternately and repeatedly With hot water and with grease solvent for a period of time sufficient for the water to hydrolyze collagen and thereby to separate it from the animal substances, and the solvent to dissolve' grease and thereby separate it from the animal substances, and subsequently separating the grease-laden solvent from the Water containing hydrolyzed collagen, the said solvent being a petroleum-base hydrocarbon solvent.

16. A method of deriving grease, and a material of the class consisting of gelatin and glue, from animal substances containing grease and col-` lagen, which method comprises, treating the animal substances alternately and repeatedly with hot Water and with substantially water immiscible grease solvent for a period of time sufiicient for the water to hydrolyze collagen and thereby to separate it from the animal substances, and the solvent to dissolve grease and thereby separate it from the animal substances, and subsequently separating the grease-laden solvent kfrom the Water containing hydrolyzed collagen, the temperature of the hot water being substantially 1 to 210 F.

17. A method 'of deriving glue and grease from bones, which method com-prises, subjecting the bones under super-atmospheric pressure alternately and repeatedly to Water at a temperature suiiicient to convert collagen of the bones to glue, and to a substantially water immiscible greasereceptive solvent for a period `of time for the water to extract hydrolyzed collagen from the bones of the solvent, to extract grease therefrom,

18. The method of deriving glue and grease from animal substances containing collagen and grease, which method comprises, subjecting the animal substances under super-'atmospheric pressure alternately and repeatedly to Water at a temperature sufficient to convert collagen in the animal substances into glue, and to a substantially water immiscible grease-receptive solvent for a period of time suffi-'cient for the water to extract hydrolyzed collagen from the animal substances, and *the solvent to extract grease therefrom.

REUBEN S. TOUR.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 276,256 Mathieu Apr. 24, 1883 1,503,751 Dreymann Aug. 5, 1924 1,556,598 Hanglin Oct. 13, 1925 2,301,242 Billaudot Nov. 10, 1942 

12. THE METHOD OF DERIVING GLUE AND GREASE FROM ANIMAL SUBSTANCES WHICH PREVIOUSLY HAVE BEEN LIMED, WHICH METHOD COMPRISES, WASHING THE ANIMAL SUBSTANCES IN WATER WHICH RESIDES IN LAYER RELATIONSHIP TO SUBSTANTIALLY WATER IMMISCIBLE GREASE-RECEPTIVE SOLVENT, AND THEREBY RE MOVING LIME FROM THE ANIMAL SUBSTANCES AND PARTIALLY LIBERATING GREASE THEREFROM, REMOVING THE WASH WATER, NEUTRALIZING THE HIDE STOCK WHILE IT IS IN CONTACT WITH THE SOLVENT, SUBSEQUENTLY COOKING THE ANIMAL SUBSTANCES IN WATER AT TEMPERATURES SUFFICIENT TO CONVERT COLLAGEN PRESENT IN THE ANIMAL SUBSTANCES INTO GELATIN, WHILE REPEATEDLY AND SUCCESSIVELY EXPOSING THE ANIMAL SUBSTANCES DURING COOKING TO THE WATER AND TO THE GREASE-RECEPTIVE SOLVENT, THEREBY COMPLETING LIBERATION OF GREASE FROM THE ANIMAL SUBSTANCES AND SIMULTANEOUSLY CONVERTING COLLAGEN TO GELATIN, AND FINALLY SEPARATING THE GREASE-LADEN SOLVENT FROM THE GELATIN-LADEN WATER. 